1. Field of the Art
This invention relates to an ultrasound diagnostic instrument to be used in medical fields for examination of internal body tissues, and more particularly to an electronic scan type ultrasound diagnostic instrument incorporating an array of a large number of ultrasound transducer elements to be sequentially driven for simultaneous or delayed transmit/receive actions.
2. Prior Art
Ultrasound diagnostic devices have been in use in medical fields for examination of internal body tissues of patients. Ultrasound diagnostic devices are arranged as a device for acquiring topographic ultrasound images of internal body tissues by processing echo signals of ultrasound pules which have been transmitted from ultrasound transducer elements toward an internal body portion of particular interest. Ultrasound transducer elements are arranged to make a scan over a predetermined range, either in a mechanical scan or in an electronic scan.
In the case of an electronic scan type ultrasound diagnostic device, for example, an ultrasound transducer is constituted by a large number of transducer elements which are arranged in a linear shape, arcuate shape or cylindrical shape or in a planar-array matrix. An ultrasound scan is made by locating the ultrasound transducer at a predetermined position and sequentially driving the ultrasound transducer elements one after another. In some cases, for transmitting ultrasound pulses in a certain beam diameter or for focusing ultrasound pulses to a certain depth, ultrasound pulses are transmitted from a plural number of transducer elements simultaneously or with predetermined time lags.
In this connection, in the case of an ultrasound transducer which is constituted by a large number of transducer elements as mentioned above, there has been a problem, in addition to complication in construction, in that it is inevitable to provide a cable of a large diameter containing a bundle of a large number of hard-wires for making wring connections to and from the respective transducer elements. Let alone transmission of ultrasound pules from outside a patient's body, the use of a thick cable is undesirable for an ultrasound probe having an ultrasound transducer at the fore end of an insert portion to be introduced into a body cavity of a patient, because the thick cable will not only degrade maneuverability of the probe at the time of insertion into a patient's body but cause greater pains on the part of the patient.
Regarding a wiring system for a large number of arrayed transducer elements, attempts have been made to reduce the number of wires by dividing transducer elements in an array into groups except those transducer elements which are driven simultaneously or with predetermined time delays (hereinafter referred to as “transducer elements interrelated for simultaneous or delayed actions”), and using common wires to the transducer groups, for example, as disclosed in Japanese Laid-Open Patent Application 2003-319938. Namely, according to this prior art, wiring connections are made to a large number of arrayed transducer elements by the use of switching elements. Signal lines to the transducer elements in an array are short circuited at every six or sixteen transducer elements.
The above-mentioned prior art wiring system succeeded in reducing the number of wires, but still has a problem that the use of switching elements for the respective signal lines results in an ultrasound transducer which is more complicated in construction and larger in size. Therefore, if the ultrasound transducer is incorporated into an insertion type ultrasound diagnostic instrument, a fore end portion of an insertion tube will become too bulky in consideration of maneuverability of the instrument at the time of insertion into a body cavity.